It’s been a lively time at the U.S. Open Tennis Championships (taking place until September 11) at the USTA Billie Jean King National Tennis Center in New York. Here, a good number of the star tennis players are also watch brand ambassadors. Here we bring you a quick look at what those still in the game (and some who are out already) are wearing (including Stan Wawrinka’s hot pink).

Both Stan Wawrinka and Serena Williams are brand ambassadors for Audemars Piguet and they are still in the running for championship status. These two athletes wear their watches on the court. Wawrinka, though, is making this year’s USTA Championships even more intriguing by the fact that he is wearing a hot pink watch strap on his timepiece.

Wawrinka wears an Audemars Piguet Royal Oak Offshore with slate gray dial, and has had the brand make him a dark pink custom strap to coordinate with his attire.

Those who follow tennis may recall the last pink worn by a male tennis star and causing a stir to be the pink lipstick that the young and rebellious Andre Agassi wore on court. Wawrinka’s reasoning is more balanced. It seems he worked with Audemars Piguet to have the brand custom make a watch strap for him that color coordinates to match his sneakers and uniform. It is an interesting color to be sure, but it pairs well with the dark anthracite gray $26,000 Royal Oak Offshore Chronograph that he wears.

Serena Williams – who has collected her 308th grand slam win — has not had to go to these lengths to color coordinate, as her Audemars Piguet Royal Oak Offshore Chronograph is fitted with a white strap. The $43,600 watch also boasts some diamonds for added flair.

Kei Nishikori is a TAG Heuer brand ambassador

Other tennis stars who are still in the game and are also watch brand ambassadors wear their watches off the court. These include Kei Nishikori, who wears a TAG Heuer, and Novak Djokovic, who wears a Seiko Astron GPS Solar Novak Djokovic Limited Edition watch.

Rolex also has a host of tennis stars who, while they don’t wear their watches on the courts, are still in the US Open play — including Jo-Wilfried Tsonga, Ana Ivanovic, and Caroline Wozniacki.

And then there are those who are out – due to injuries or loss – who are also watch brand ambassadors. Foremost on the list is Richard Mille ambassadors, Rafael Nadal – out due to injury – but who wears his $775,000 RM 27-02 Tourbillon Rafael Nadal watch during play. Roger Federer, also out due to injury, is a Rolex brand ambassador. Borna Coric, who lost early in the Open, is a Hublot brand ambassador, wearing a Big Bang Ferrari.

Oh, and let’s not forget that Citizen is the presenting sponsor of the US Open Tennis Championships — with a pervasive presence on the court. This brand has been the Official Timekeeper of the US Open Tennis Championships for 24 years, where the match time displays have recorded some of the longest Grand Slam matches in history.

Citizen Watch Company has been the Official Timekeeper of the US Open Tennis Championships for 24 years.